Using an exponential function, it is found that the city will be half populated in 9 months.
The population of Fantasy City doubles each month, hence, after t months, the population is given by:
[tex]P(t) = P(0)2^{t}[/tex]
Fully populated in 10 months, hence, the full population is:
[tex]P(10) = P(0)2^{10} = 1024P(0)[/tex]
Hence, half populated is [tex]P(t) = \frac{1024P(0)}{2} = 512P(0)[/tex], hence:
[tex]P(t) = P(0)2^{t}[/tex]
[tex]512P(0) = P(0)2^{t}[/tex]
[tex]2^t = 512[/tex]
[tex]2^t = 2^9[/tex]
[tex]t = 9[/tex]
The city will be half populated in 9 months.
To learn more about exponential functions, you can take a look at https://brainly.com/question/25537936